Truck just sitting?

A battery tender helps. I have a small solar powered one in the window of the garage plugged into the cigarette lighter socket that keeps me topped off.

Dual battery Silverado 2500HD here (non diesel). Our truck sits in storage for 7 to 8 months a year (this year an early spring, so only 6 months storage). I stopped using the battery minder probably, hmmm, 8 years ago. I now just disconnect my 2 batteries for storage (it takes me only ~2 minutes to disconnect them), and I disconnect them if we have no driving planned for more than a week. The truck is a 2004.5; and starter battery is still original. After 12 years, it is still like nearly new condition. I've only replaced the accessory battery; that was done last year (at 11 years old) LOL!

...OK, back to the program...